We report our experiences with conducting ptychography simultaneously with Xray fluorescence measurement using the on-the-fly mode for efficient multi-modality imaging. We demonstrate that the periodic artifact inherent to the raster scan pattern can be mitigated using a sufficiently fine scan step size to provide an overlap ratio > 70%. This allows us to obtain transmitted absorption and phase contrast images with enhanced spatial resolution from ptychography while maintaining the fluorescence imaging with continuous-motion scans on pixelated grids. This capability will greatly improve the competence and throughput of scanning probe X-ray microscopy. Scanning probe X-ray microscopy is a powerful imaging method that simultaneously evokes multiple contrast mechanisms, including absorption, phase, fluorescence, diffraction and spectroscopy. These signals carry versatile information, and enable a suite of analytical tools to reveal a comprehensive view of the specimen under study. Correlative imaging using multiple contrast mechanisms simultaneously can significantly leverage the information obtained in the images. With the steady progress on fabricating high-resolution X-ray optics [1-5] and developing advanced microscopes [6-8], the achievable spatial resolution and detection sensitivity is continuously improving. Ptychography [9], as a scanning version of coherent diffraction imaging method, shares almost the same data acquisition scheme as a typical scanning probe microscope measurement, such as scanning X-ray transmission microscope (STXM) [10]. By scanning the specimen across a confined illumination

The highly convergent x-ray beam focused by multilayer Laue lenses with large numerical apertures is used as a threedimensional (3D) probe to image layered structures with an axial separation larger than the depth of focus. Instead of collecting weakly scattered high-spatial-frequency signals, the depth-resolving power is provided purely by the intense central cone diverged from the focused beam. Using the multi-slice ptychography method combined with the on-the-fly scan scheme, two layers of nanoparticles separated by 10 μm are successfully reconstructed with 8.1 nm lateral resolution and with a dwell time as low as 0.05 s per scan point. This approach obtains high-resolution images with extended depth of field, which paves the way for multi-slice ptychography as a high throughput technique for high-resolution 3D imaging of thick samples.

The results of a systematic rigorous study on the accuracy of lattice parameters computed from X-ray diffraction patterns of ideally perfect nanocrystalline powder and thin-film samples are presented. It is shown that, if the dimensions of such samples are below 20 nm, the lattice parameters obtained from diffraction analysis will deviate from their true values. The relative deviation depends on the relevant size parameter through an inverse power law and, for particular reflections, depends on the angular peak positions. This sizedependent error, Áa/a, is larger than the precision of typical X-ray diffraction measurements for $20 nm-thick diffracting domains, and it can be several orders of magnitude larger for particles smaller than 5 nm. ISSN 1600-5767# 2018 International Union of Crystallography l -edge length of a cube-shaped crystal. m -exponential factor. L A -number of populated lattice points in a crystallite. ðrÞ -local electron density function in a crystal being illuminated. 1 ðrÞ -triply periodic infinite electron density. yðrÞ -shape function.YðqÞ -Fourier transform of yðrÞ. F hkl -structure factor. H -reciprocal space vector. cell -volume of a unit cell. t f -thickness of a thin film. V Crystal -volume of a crystal being illuminated. d hkl -atomic plane spacing of the diffracting crystal planes. A p -amplitude scattered by an atomic plane of thickness d hkl .-dispersion parameter in a Gaussian function. C -Scherrer shape parameter.

In this study, we present a numerical framework for modeling three-dimensional (3D) diffraction data in Bragg coherent diffraction imaging (Bragg CDI) experiments and evaluating the quality of obtained 3D complex-valued real-space images recovered by reconstruction algorithms under controlled conditions. The approach is used to systematically explore the performance and the detection limit of this phase-retrieval-based microscopy tool. The numerical investigation suggests that the superb performance of Bragg CDI is achieved with an oversampling ratio above 30 and a detection dynamic range above 6 orders. The observed performance degradation subject to the data binning processes is also studied. This numerical tool can be used to optimize experimental parameters and has the potential to significantly improve the throughput of Bragg CDI method.

Multi-slice X-ray ptychography offers an approach to achieve images with a nanometre-scale resolution from samples with thicknesses larger than the depth of field of the imaging system by modeling a thick sample as a set of thin slices and accounting for the wavefront propagation effects within the specimen. Here, we present an experimental demonstration that resolves two layers of nanostructures separated by 500 nm along the axial direction, with sub-10 nm and sub-20 nm resolutions on two layers, respectively. Fluorescence maps are simultaneously measured in the multi-modality imaging scheme to assist in decoupling the mixture of low-spatial-frequency features across different slices. The enhanced axial sectioning capability using correlative signals obtained from multi-modality measurements demonstrates the great potential of the multi-slice ptychography method for investigating specimens with extended dimensions in 3D with high resolution.